Hitherto, as curing agents that exhibit a low-temperature fast-curing activity with respect to epoxy resins, there have been proposed aluminum chelate-based latent curing agents in which porous resins obtained by interfacial polymerization of multifunctional isocyanate compounds support aluminum chelate-based curing agents (for example, see PTLs 1 to 3).
However, there is a problem that thermosetting epoxy resin compositions containing the latent curing agents of the proposed techniques tend to undergo viscosity rise during storage.
When the proposed techniques are employed, an attempt to suppress viscosity rise during storage results in degradation of low-temperature curability.
Hence, under the current circumstances, a latent curing agent that can satisfy both of a low-temperature curing ability and suppression of viscosity rise of thermosetting epoxy resin compositions during storage is demanded.